Control circuits for induction motors



Oct. 19, 1954 J. w s 2,692,362

CONTROL CIRCUITS FOR INDUCTION MOTORS Filed July 23, 1953 2 Sheets-Sheet l OFF/ REvERsE P FORWARD //0 v A0 J SATUR/IBLE 2/0 FF W 176. 2 REvERsE c; FORWARD INVENTOR. Alexander J Lewus Oct. 19, 1954 J wus 2,692,362

CONTROL. CIRCUITS FOR INDUCTION MOTORS Filed July 23, 1953 2 Sheets-Sheet 2 REvERsE OFF FORWARD //0 V 35 1 A 326 5/1 TURABLE 336 33 303 GEE 1 360 FIG 4 L a //0 v [W FORWARD FIG 3 k z. \O'42/ JAE,

407 L54 TURABLE INVENTOR. Alexander J Lewus M,%M,Mmm

Ally;

Patented Oct. 19, 1954 OFFICE CONTROL CIRCUITS FOR INDUCTION MOTORS Alexander J. Lewus, Cicero, Ill. Application July 23, 1953, Serial No. 369,853

14 Claims. 1

The present invention relates to control circuits for induction motors and more particularly to such circuits for induction motors of the capacitor type disclosed in the copending application of Alexander J. Lewus, Serial No. 360,798, filed June 10, 1953.

It is the general object of the present invention to provide in a circuit of the character noted, a circuit controller or switch that is selectively operative between an off position and forward and reverse positions for the purpose of selectively starting and running the rotor of the associated induction motor in the respective forward and reverse directions, wherein the switch is arranged to disconnect the windings of the motor from the associated source of power supply when it is returned from either its forward position or its reverse position back into its off position.

Another object of the invention is to provide a circuit controller or switch in a circuit of the character noted, wherein the switch is also arranged to complete a dynamic braking circuit for the rotor when the switch is returned from either its forward position or its reverse position back into its off position so that the direction of rotation of the motor may be instantly reversed.

A further object of the invention is to provide a circuit controller or switch in a circuit of the character noted, wherein the forward and reverse positions of the switch comprise final positions disposed on the opposite sides of the intermediate off position thereof, so that the rotor is stopped instantly and reversed instantly when the switch is quickly operated from one of its final positions to the other of its final positions through its intermediate position.

A further object of the invention is to provide a circuit controller or switch for starting and running and braking the reversible rotor of an induction motor of the single-phase split-phase type, including a stator provided with angularly displaced main and auxiliary windings, wherein the auxiliary winding and an associated capacitor are employed for starting the rotor in either direction, and wherein the auxiliary winding and at least a portion of the associated capacitor are employed for braking the rotor when the switch is returned from either its forward position or its reverse position back into its off position.

A still further object of the invention is to provide a starting and running and braking control circuit for the reversible rotor of an induction motor of the single-phase split-phase type, including a stator provided with angularly displaced main and auxiliary windings, wherein the circuit includes a circuit controller or switch having an oil position and forward and reverse positions, as well as a transformer provided with a core having primary and secondar windings, wherein the switch in its forward and reverse positions completes a first circuit for energizing in series relation the main winding and the primary winding, while a second circuit is completed for energizing in series relation the auxiliary winding and the secondary winding via an associated capacitor, and wherein the switch in its respective forward and reverse positions effects corresponding poling of the elements included in one of the first and second circuits for starting and running of the rotor in the corresponding directions.

Further features of the invention pertain to the particular connection and arrangement of the elements of the electric motor and of the transformer and of the circuit controller or switch, whereby the above-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic illustration of a starting-running control circuit for a single-phase split-phase induction motor of the capacitor type and embodying the present invention;

Fig. 2 is a diagrammatic illustration of a modified form of the control circuit of Fig. 1;

Fig. 3 is a diagrammatic illustration of a starting-running-braking control circuit for an induction motor of the type noted; and

Fig. 4 is a diagrammatic illustration of a modified form of the control circuit of Fig. 3.

Referring now to Fig. 1 of the drawings, there is illustrated a starting-running control circuit embodying the features of the present invention and comprising an electric motor I00 of the single-phase split-phase induction type including a stator HH provided with angularly displaced main and auxiliary windings I02 and I03, and a reversible rotor I04 provided with a squirrelcage Winding I05. Also the control circuit includes a transformer I06 provided with a saturable magnetic core I01 carrying primary and secondary windings I08 and I89. Further, the circuit comprises a circuit controller or switch HU having an intermediate off position and forward and reverse positions disposed on opposite sides of the off position. Finally, the circuit com- 3 prises a capacitor III, that is preferably of the dry electrolytic type, and a source of current supply of 110 volts single-phase A. C. In the arrangement, the switch I I includes three movable blades H2, H3 and H4 cooperating with corresponding pairs of stationary contacts II-II6, IIlI I8 and II9-I20, the contacts H5, H1 and H9 constituting reverse contacts and the contacts H6, H8 and I20 constituting forward contacts. Of course, the switch I I0 may be operated either manually or automatically in a conventional manner.

Considering now the operation of the motor I00, when the switch I I0 occupies its off position, the main and auxiliary windings I02 and I03, as well as the primary and secondary windings I 08 and I09, are deenergized.

When the switch H0 is operated into its forward position, the blades H2, H3 and H4 complete, at the respective forward contacts H6, H8 and I20, a first circuit for energizing in series relation the primary winding I08 and the main winding I02 across the source of current supply. Also at this tim a second or local circuit is completed for energizing in series relation the secondary winding I09 and the auxiliary winding I03 via the capacitor H I. Further, at this time the primary winding I08 and the main winding I02 are poled with respect to each other in the forward direction so that the relatively heavy starting currents respectively traversing the main windin I02 and the auxiliary winding I03 efiect starting of the rotor I04 in the forward direction, the capacitor III effecting the necessary phase-shift between the starting currents respectively traversing the main and auxiliary windings I02 and I03. Hence the rotor I04 is accelerated in the forward direction and ultimately rotates at its norma1 running speed somewhat below the synchronous speed. During normal forward running of the rotor I04, the current traversing the main winding I02 is modest and the current traversing the auxiliary winding I03 is exceedingly small; whereby it is unnecessary to open the local circuit, including the secondary winding I09, the auxiliary winding I03 and the capacitor III.

On the other hand, when the switch I I0 is operated into its reverse position, the blades H2,

H3 and H4 complete, at the respective reverse contacts H5, H1 and H9, the first circuit for energizing in series relation the primary winding I00 and the main winding I02 across the source of current supply. Also at this time the second or local circuit is completed for energizing in series relation the secondary winding I09 and the auxiliary winding I03 via the capacitor II I. Further, at this time th primary winding I08 and the main winding I02 are poled with respect to each other in the reverse direction so that the relatively heavy starting currents respectively traversing the main winding I02 and the auxiliary winding I03 effect starting of the rotor I04 in the reverse direction, the capacitor III efiecting the necessary phase-shift between the starting currents respectively traversing the main and auxiliary windings I02 and I03. Hence the rotor I04 is accelerated in the reverse direction and ultimately rotates at its normal running speed somewhat below the synchronous speed. Dllllllg normal reverse running of the rotor I04, the current traversing the main winding I02 is modest and the current traversing the auxiliary windin I03 is exceedingly small; whereby it is unnecessary to open the local circuit, including the secondary 4 winding I09, the auxiliary winding I03 and the capacitor III.

In connection with the poling of the primary winding I08 and the main winding I02 with respect to each other in the corresponding forward and reverse positions of the switch H0, it is noted that the terminals of the primary winding I08 are actually reversed; however, alternatively the terminals of the main winding I02 may be reversed in order to eifect reversal of the relative poling or the main winding I02 and the primary winding I08 in an obvious manner.

Considering now in greater detail the construction and arrangement of the motor I00 and the transformer I06, the motor I00 may be of the fractional horsepower type or may have a rating as high as about 10 hp., and the magnetic core IN or the transformer I06 is of the saturable type. In the illustrated embodiment, the motor I00 has a rating of one hp.; whereby the main winding I02 comprises 400 turns; the auxiliary winding I03 comprises turns; the primary winding I08 comprises 84 turns; and the secondary winding I09 comprises 233 turns. Accordingly, the starting and running impedances of the main winding I02 are respectively low and high with respect to each other so that the magnetic core I01 is respectively saturated and unsaturated by the respective starting and running currents traversing the primary winding I08; whereby the starting and running currents traversing the primary winding I00 respectively induce peaked starting and substantially sinusoidal running voltages in the secondary winding I09. The starting and running voltages induced in the secondary winding I09 are harmonically distorted and are respectively high and low with respect to each other, and the starting and running impedances of the auxiliary winding I03 are respectively low and high with respect to each other, so that the starting and running currents traversing the auxiliary winding I03, are respectively high and low with respect to each other. The starting current traversing the primary Winding I08 maintains saturated the magnetic core I01 from standstill to at least 50% of the normal running speed of the rotor I04, the rotor I00 having a normal running speed at full load of about 1735 R. P. M. and a synchronous speed of 1800 R. P. M.

More particularly, from standstill to about 50% of the normal running speed of the rotor I04, the rotor I04 develops at least normal torque, the starting torque increasing rapidly from this speed to approximately 275% normal torque at 67% of the normal running speed thereof, and then decreasing gradually to 100% normal torque at the normal running speed thereof. The capacitor I I I has a relatively small capacitance (about 230 microfarad) and a relatively high voltage rating (about 200 volts). The second or local circuit, including the auxiliary winding I03, the secondary winding I09 and the capacitor III, is substantially series resonant during saturation of the magnetic core I0'I so that the capacitor III eifects substantially dephasing of the starting current traversing the auxiliary winding I03 with respect to the starting current traversing the main winding I02 in order to produce a substantial starting torque between the stator IOI and the rotor I04, as described above. When the rotor I00 is rotated at its normal full load running speed of about 1735 R. P. M. the voltage induced in the auxiliary winding I03 from the main winding I02 is in opposition to the voltage induced in the secondary winding !09 from the primary winding !08; whereby there is substantially no resulting voltage in the second or local circuit so that the current traversing the capacitor ill is exceedingly small.

Referring now to Fig. 2, a modified form of the control circuit is illustrated that includes corresponding elements, including the motor 200, the transformer the circuit controller or switch 2!!! and the capacitor 2, the motor 200 including the main and auxiliary windings 232 and 233, as well as the rotor 234 carrying the squirrel-cage winding 205, the transformer 236 including the primary and secondary windings 208 and 239. In this arrangement, the switch 2 I is provided with an intermediate off position and forward and reverse positions disposed on opposite sides of the off position. Further, the switch 2H1 comprises four blades provided with cooperating pairs of contacts arranged in forward and reverse groups.

The operation of the motor 233 is generally the same as that of the motor described above; however, in this case, the switch file effects relative poling between the auxiliary winding 233 and the secondary winding 3533, the terminals of the auxiliary winding being reversed incident to operation. of the switch 253 between its forward and reverse positions. It is noted that the relative poling of the auxiliary winding 233 and the secondary winding with respect to each other may alternatively be achieved by reversing the terminals of the secondary winding 209 incident to operation of the switch 2h! between its forward and reverse positions.

In any case, the rotor 23 i is started and run in its respective forward and reverse directions in response to operation of the switch Eli? into its respective forward and reverse positions; the circuit conditions incident to starting and run ning of the motor 233 being identical to those described above in conjunction with the motor I00.

Referring now to Fig. 3, a further modified form of the control circuit is illustrated that generally corresponds to l and that includes the motor the transformer the circuit controller or switch and the capacitor 3lla3iib, the motor 333 including the main and auxiliary windings and 303, as

well as the rotor 33 i carrying the squirrel-cage winding 335, and the transformer including the saturable magnetic core carrying the primary and secondary windings 333 and 303. In this arrangement the switch 3M3 is in the form of a drum controller having an intermediate off position and forward and reverse positions disposed on opposite sides of the OE position. Specifically, the drum controller 3m includes a set of seven stationary contacts fail to 321, inclusive; a set of two off contacts or slides 336 and 33?; a set of five forward contacts or slides 34! to 345, inclusive; and a set of iive reverse contacts or slides 35f to inclusive.

In the arrangement of the drum controller 3 0, the stationary contacts to 335, inclusive, respectively engage the forward contacts 34! to 345, inclusive, when the drum is rotated into its forward position, and the stationary contacts 32! to 325, inclusive, respectively engage the reverse contacts 355 to inclusive, when the drum is rotated into its reverse position. Finally, the stationary contacts 32b to 327 engage the off contacts 333 and 3% when the drum is rotated into its oil" position and during a small overlap are of its respective forward and reverse positions. In other words, when the drum is rotated from its off position into its forward position, the stationatry contacts 32! to 325, inclusive, engage the respective forward contacts 34! to 365, inclusive, shortly before the stationary contacts 326 and 32! respectively disengage the off contacts 338 and 331; and a reverse operation takes place when the drum is rotated from its forward position back into its off position. Similarly when the drum is rotated from its off position into its reverse position, the stationary contacts 32! to 325, inclusive, engage the respective reverse contacts 35! to 355, inclusive, shortly before the stationary contacts 325 and 327 respectively disengage the off contacts 335 and 331; and a reverse operation takes place when the drum is rotated from its reverse position back into its off position.

It is noted that the capacitor is divided into two sections 3! la and 3H1), and that a control switch 303 is provided that may be selectively operated to short-circuit the section 3H1) of the capacitor, for a purpose more fully explained hereinafter.

The control circuit of Fig. 3 corresponds generally to that of Fig. 1, as previously noted, but this control circuit also embodies an arrangement for dynamically braking the rotor 304 of the motor 300 incident to the return of the drum controller 3!0 from either its forward position or its reverse position back into its off position. Specifically, when the drum controller 3m is operated from its off position into its forward position, the rotor 304 of the motor 305 starts and then runs in the forward direction, the primary winding 308 of the transformer 30% being poled for the forward starting by virtue of the cooperation between the stationary contacts 324 and 325 and the respectively engaged forward contacts 344 and 345. Subsequently, when the drum controller 3? is returned from its forward position back into its off position, the stationary contacts 326 and 32'! respectively engage the off contacts 336 and 33'! during a short are of the return movement while the stationary contacts 32! to 325, inclusive, respectively engage the forward contacts 3 3! to 345, inclusive. Accordingly, the auxiliary winding 303 is short-circuited during this short time interval, while the main winding 332 is energized; whereby the rotor 304 is dynamically braked, the rotation thereof being arrested substantially instantly. The path for short-circuiting the auxiliary winding 303 includes the stationary contacts 326 and 32'! and the respectively engaged off contacts 336 and 331; and may include or exclude the section 3i lb of the capacitor, depending upon the position of the control switch 300. Normally, the inclusion of the section 3! lb of the capacitor in the path for short-circuiting the auxiliary winding 303, when the control switch 383 occupies its open position, effects a reduction in the braking rate of the rotor 304. Also in passing, it is noted that a multiple path is completed for short-circuiting the secondary winding 309 that includes the section 3! la of the capacitor; whereby the secondary winding 309 is protected against unduly heavy short-circuit currents prior to the operation of the drum controller 3!0 into its off position to interrupt the first circuit for energizing in series relation the primary winding 308 and the main winding 302.

Similarly, when the drum controller 3! 0 is operated from its oil position into its reverse position the rotor 304 of the motor 300 starts and then runs in the reverse direction, the primary winding 308 of the transformer 306 being poled for the reverse starting by virtue of the cooperation between the stationary contacts 324 and 325 and the respectively engaged reverse contacts 354 and 355. Subsequently when the drum controller 3!!) is returned from its reverse position back into its off position, the stationary contacts 326 and 321 respectively engage the off contacts 336 and 331 during a short arc of the return movement, while the stationary contacts 32! to 325, inclusive, respectively engage the reverse contacts 35! to 355, inclusive. Accordingly, the auxiliary winding 303 is short-circuited during this short time interval while the main winding 302 is energized; whereby the rotor 304 is dynamically braked, the rotation thereof being arrested substantially instantly. The path for short-circuiting the auxiliary winding 303 and the multiple path for short-circuiting the secondary winding 309 are the same as described above; and the braking rate of the rotor 304 again depends upon the position of the control switch 360.

In conjunction with the control circuit of Fig. 3, it is noted that the reverse poling of the primary winding 308 with respect to the main winding 302 is achieved by reversing the terminals of the primary winding 308, but that alternatively this effect may be obtained by reversing the terminals of the main winding 302.

In view of the above description, it will be understood that the drum controller 3!0 may be quickly operated from either of its extreme posi tions through its off position into the other of its extreme positions so as to effect reversal of the direction of rotation of the rotor 304 with dynamic braking therebetween; whereby the drum controller 3l0 may be quickly or instantly operated between its extreme positions without any danger of damage to the motor 300 and so as to obtain the required reversal of the direction of rotation of the rotor 304.

Referring now to Fig. 4, a further modified form of the control circuit is illustrated that generally corresponds to Fig. 2 and that includes the motor 400, the transformer 406, the circuit controller or switch M0, and the capacitor 4i !a4! lb, the

motor 400 including the main and auxiliary winding 402 and 403, as well as the rotor 404 carrying the squirrel-cage winding 405, and the transformer 406 including the saturable magnetic core 401 carrying the primary and secondary windings 408 and 409. In this arrangement, the switch M is in the form of a drum controller having an intermediate olf position and forward and reverse positions disposed on opposite sides of the off position. Specifically, the drum controller M0 includes a set of eight stationary contacts 42! to 428, inclusive; a set of two oif contacts or slides 431 and 438; a set of six forward contacts or slides 44! to 446, inclusive; and a set of six reverse contacts or slides 45! to 456, inclusive.

In the arrangement of the drum controller M0, the stationary contacts 42! to 426, inclusive,

respectively engage the forward contacts 44! to rotated from its 01f position into its forward position, the stationary contacts 42! to 426, inclusive, engage the respective forward contacts 44! to 446, inclusive, shortly before the stationary contacts 421 and 428 respectively disengage the off contacts 431 and 438; and a reverse operation takes place when the drum is rotated from its forward position back into its off position. Similarly, when the drum is rotated from its off position into its reverse position the stationary contacts 42l to 426, inclusive, engage the respective reverse contacts 45! to 456, inclusive, shortly before the stationary contacts 421 and 428 respectively disengage the off contacts 431 and 438; and a reverse operation takes place when the drum is rotated from its reverse posi tion back into its off position.

It is noted that the capacitor is divided into two sections 4! la and 4! lb, and that a control switch 460 is provided that may be selectively operated to short-circuit the section 4! lb of the capacitor, for a purpose more fully explained hereinafter.

The control circuit of Fig. 4 corresponds generally to that of Fig. 2, as previously noted, but this control circuit also embodies an arrangement for dynamically braking the rotor 404 of the motor 400 incident to the return of the drum controller 4!!) from either its forward position or its reverse position back into its 01? position. Specifically, when the drum controller M0 is operated from its olT position into its forward position, the rotor 404 of the motor 400 starts and then runs in the forward direction, the auxiliary winding 403 of the motor 400 being poled for the forward starting by virtue of the cooperation between the stationary contacts 425 and 426 and the respectively engaged forward contacts 445 and 446. Subsequently when the drum controller M0 is returned from its forward position back into its off position, the stationary contacts 421 and 428 respectively engage the ofi contacts 431 and 438 during a short are of the return movement while the stationary contacts 42! to 42 6, inclusive, respectively engage the forward contacts 44! to 446, inclusive. Accordingly, the auxiliary winding 403 is short-circuited during this short time interval, while the main winding 402 is energized; whereby the rotor 404 is dynamically braked, the rotation thereof being arrested substantially instantly. The path for short-circuiting the auxiliary winding 403 includes the stationary contacts 421 and 428 and the respectively engaged off contacts 431 and 438; and may include or exclude the section 4! lb of the capacitor, depending upon the position of the control switch 460. Normally, the inclusion of the section 4! lb of the capacitor in the path for short-circuiting the auxiliary winding 403, when the control switch 460 occupies its open position, effects a reduction in the braking rate of the rotor 404. Also, in passing, it is noted that a multiple path is completed for shortcircuiting the secondary winding 409 that includes the section 4i la of the capacitor; whereby the secondary winding 409 is protected against unduly heavy short-circuiting currents prior to the operation of the drum controller 4!0 into its off position to interrupt the first circuit for energizing in series relation the primary winding 408 and the main winding 402.

Similarly, when the drum controller M0 is operated from its off position into its reverse position, the rotor 404 of the motor 400 starts and then runs in the reverse direction, the

' 9 auxiliary winding 403 of the rotor 400 being poled for the reverse starting by virtue of the cooperation between the stationary contacts 425 and 426 and the respectively engaged reverse contacts 455 and 456. Subsequently when the drum controller 410 is returned from its reverse position back into its on" position, the stationary contacts 421 and 428 respectively engage the off contacts 431 and 438 during a short are of the return movement, while the stationary contacts 42! and 426, inclusive, respectively engage the reverse contacts 45! to 456, inclusive. Accordingly, the auxiliary winding 403 is short-circuited during this short time interval while the main winding 402 is energized; whereby the rotor 404 is dynamically braked, the rotation thereof being arrested substantially instantly. The path for short-circuiting the auxiliary winding 403 and the multiple path for short-circuiting the secondary winding 409 are the same as described above; and the braking rate of the rotor 404 again depends upon the position of the control switch 460.

In conjunction with the control circuit of Fig. 4, it is noted that the reverse poling of the auxiliary winding 403 with respect to the secondary winding 409 is achieved by reversing the terminals of the auxiliary winding 403, but that alternatively this eifect may be obtained by reversing the terminals of the secondary winding 409.

In view of the above description, it will be understood that the drum controller 4l0 may be quickly operated from either of its extreme positions through its off position into the other of its extreme positions so as to effect reversal of the direction of rotation of the rotor 404 with dynamic braking therebetween; whereby the drum controller H may be quickly or instantly operated between its extreme positions without any danger of damage to the motor 400 and so as to obtain the required reversal of the direction of rotation of the rotor 404.

In connection with the drum controllers SW and 4m in the respective control circuits of Figs. 3 and 4:, itis pointed out that it is conventional to bias such a drum controller by means, not shown, into its off position, and to provide restraining means, not shown, to retain the same in each of its forward and reverse positions; and in the drum controllers Siti'and 4l0 such facilities may be incorporated if desired.

In view of the foregoing, it is apparent that there has been provided improved startingrunning control circuits for induction motors of the single-phase split-phase capacitor type that insure ready starting and running of the rotors in either direction, as well as improved startingrunning-braking control circuits for such motors that further insure positive reversal of the direction of rotation of the rotors and dynamic braking therebetween incident to operation of the associated circuit controllers between their corresponding forward and reverse positions.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a control circuit including an induction motor provided with a stator having angularly displaced main and auxiliary windings and a reversible rotor having a squirrel-cage winding, a transformer provided with a core having primary and secondary windings, a capacitor, and a source of single-phase alternating current supply; the combination comprising a control switch having an off position and forward and reverse positions respectively disposed on opposite sides of said off position, means for selectively operating said switch between its different positions, a first circuit for energizing said main winding and said primary winding in series relation across said source, said switch in its off position interrupting said first circuit and in either its forward position or its reverse position completing said first circuit, a second circuit for connecting said auX- iliary winding and said secondary winding and said capacitor in series relation, and means controlled by operation of said switch between its forward and reverse positions for reversing the relative polarity between one of said transformer windings and one of said motor windings in the corresponding one of said circuits so that said rotor starts and runs in the forward direction when said switch is operated into its forward position and so that said rotor starts and runs in the reverse direction when said switch is operated into its reverse position.

2. In a control circuit including an induction motor provided with a stator having angularly displaced main and auxiliary windings and a reversible rotor having a squirrel-cage winding, a transformer provided with a core having primary and secondary windings, a capacitor, and a source of single-phase alternating current supply; the combination comprising a control switch having an off position and forward and reverse positions respectively disposed on opposite sides of said off position, means for selectively operating said switch between its different positions, a first circuit for energizing said main winding and said primary winding in series relation across said source, said switch in its off position interrupting said first circuit and in either its forward position or its reverse position completing said first circuit, a second circuit for connecting said auxiliary winding and said secondary winding and said capacitor in series relation, and means controlled by operation of said switch between its forward and reverse positions for reversing the relative polarity between said primary winding and said main winding in said first circuit so that said rotor starts and runs in the forward direction when said switch is operated into its forward position and so that said rotor starts and runs in the reverse direction when said switch is operated into its reverse position.

3. In a control circuit including an induction motor provided with a stator having angularly displaced main and auxiliary windings and a reversible rotor having a squirrel-cage winding, a transformer provided with a core having primary and secondary windings, a capacitor, and a source of single-phase alternating current supply; the combination comprising a control switch having an off position and forward and reverse positions respectively disposed on opposite sides of said on position, means for selectively operating said switch between its different positions, a first circuit for energizing said main winding and said primary winding in series relation across said source, said switch in its off position interrupting said first circuit and in either its forward position or its reverse position completing said first circuit, a second circuit for connecting said auxiliary winding and said secondary winding and said capacitor in series relation, and means controlled by operation of said switch between its forward and reverse positions for reversing the relative polarity between said secondary winding and said auxiliary winding in said second circuit so that said rotor starts and runs in the forward direction when said switch is operated into its forward position and so that said rotor starts and runs in the reverse direction when said switch is operated into its reverse position.

4. In a control circuit including an induction motor provided with a stator having angularly displaced main and auxiliary windings and a reversible rotor having a squirrel-cage winding, a transformer provided with a core having primary and secondary windings, a capacitor, and a source of single-phase alternating current supply; the combination comprising a control switch having an off position and forward and reverse positions respectively disposed on opposite sides of said off position, means for selectively operating said switch between its different positions, a first circuit for energizing said main winding and said primary winding in series relation across said source, a second circuit for connecting said aux iliary winding and said secondary winding and said capacitor in series relation, means controlled by operation of said switch from its off position into its forward position for establishing a forward polarity between one of said transformer windings and one of said motor windings in the corresponding one of said circuits to condition said rotor for forward starting and controlled by operation of said switch from its off position into its reverse position for establishing a reverse polarity between said one transformer winding and said one motor winding in said one circuit to condition said rotor for reverse starting, means controlled by operation of said switch from its off position into either its forward position or its reverse position for completing said first circuit so as to effect corresponding starting and running of said rotor, a path for short-circuiting said auxiliary winding, means controlled by operation of said switch from either its forward position or its reverse position back into its off position for completing said path and then for interrupting said first circuit in order to effect dynamic braking of said rotor, and additional means controlled by operation of said switch from its off position into either its forward position or its reverse position for interrupting said path.

5. The control circuit combination set forth in claim 4, wherein said one transformer winding is said primary winding and said one motor winding is said main winding and said one circuit is said first circuit.

6'. The control circuit combination set forth in claim 4, wherein said one transformer winding is said secondary winding and said one motor winding is said auxiliary winding and said one circuit is said second circuit.

7. The control circuit combination set forth in claim 4, wherein said dynamic braking of said rotor instantly arrests rotation thereof so as to prevent overrun of said rotor when said switch is instantly operated from either its forward position or its reverse position back into its off position.

The control circuit combination set forth in claim 4, wherein said dynamic braking of said rotor instantly arrests rotation thereof so that said controller may be instantly operated between its forward position and its reverse position through its off position to effect corresponding instant reversal of the direction of rotation of said rotor.

9. The control circuit combination set forth in claim 4, wherein said path for short-circuiting said auxiliary winding includes at least a portion of said capacitor.

10. The control circuit combination set forth in claim 4, and further comprising a device selectively operative to include and to exclude a portion of said capacitor with respect to said path for short-circuiting said auxiliary winding.

11. The control circuit combination set forth in claim 4, wherein said switch is essentially in the form of a rotary drum-controller.

12. The control circuit combination set forth in claim 1, wherein said capacitor is of the dry electrolytic type.

13. The control circuit combination set forth in claim 1, wherein said transformer core is of the saturable type so that it is respectively saturated and unsaturated during starting and running of said rotor in either direction.

14. The control circuit combination set forth in claim 13, wherein said second circuit is at a near series-resonant condition during saturation of said transformer core.

No references cited. 

